Optoelectronic sensor

Abstract

Examples present an optoelectronic sensor configured to detect the presence of an object in a predetermined area by the reflection of at least one light beam. The sensor comprises: a subtractor stage configured to generate an output voltage by subtracting a second voltage generated from a second photodiode from a first voltage generated from a first photodiode following the emission of at least one beam; a summing stage configured to generate an output voltage by adding the first voltage to the second voltage. The optoelectronic sensor is configured such that the difference between a first light flux received by the first photodiode and a second flux received by the second photodiode is positive when a beam is reflected while the object is in the predetermined area; and to detect the object from the output voltages of the subtractor and summing stages. Abstract figure: [Fig. 1]

Description

Title of the invention: Optoelectronic sensor technical field

[0001] This disclosure relates to the field of optoelectronic sensors configured to detect the presence of an object in a predetermined detection zone by reflection of a light beam on that object. Previous technique

[0002] Optoelectronic sensors are now used to detect the presence of an object in a predetermined detection zone.

[0003] These sensors emit a light beam into the predetermined detection zone and monitor the electrical output signal of a photodiode in response to the light beam emission. Specifically, the electrical output signal of the photodiode is proportional to the luminous flux received by the photodiode. This electrical output signal differs depending on whether the object is within the predetermined detection zone or not, as the object will reflect the light beam emitted by the sensor. Therefore, monitoring the electrical output signal of the photodiode can detect the presence or absence of the object within the predetermined detection zone.

[0004] However, the electrical output signal of the photodiode is generally very weak, so this output signal is relatively sensitive to noise. In particular, the luminous flux surrounding the sensor and the intrinsic reflectivity of the object to be detected, which depends in part on its color, can sometimes impair the operation of the sensor.

[0005] The present disclosure improves this situation. Summary

[0006] In this regard, an optoelectronic sensor is proposed, configured to detect the presence of an object in a predetermined detection zone by reflecting at least one light beam off said object, the optoelectronic sensor comprising: - a light source suitable for emitting at least one beam of light in a predetermined direction; - a first photodiode configured to generate a first electric current as a function of a first luminous flux on the first photodiode; - a second photodiode configured to generate a second electric current based on a second luminous flux on the second photodiode; - a converter stage configured to convert the first and second electrical currents into first and second electrical voltages; - a subtractor stage configured to generate an output voltage by subtracting the second electrical voltage from the first electrical voltage; - a summing stage configured to generate an output voltage by adding the first electrical voltage to the second electrical voltage; in which the optoelectronic sensor is configured: - such that the difference between the first luminous flux received by the first photodiode and the second luminous flux received by the second photodiode is positive when a light beam is reflected by an object positioned within the predetermined detection zone; and - to detect an object from the output voltages of the subtractor stage and the summing stage.

[0007] Optionally, the optoelectronic sensor further includes a signal amplifier stage capable of amplifying the first and second electrical currents or capable of amplifying the first and second electrical voltages.

[0008] Optionally, the converter stage is also an amplifier stage and includes a first transimpedance amplifier capable of amplifying and converting the first electric current into a first electric voltage and a second transimpedance amplifier capable of amplifying and converting the second electric current into a second electric voltage.

[0009] Optionally, the optoelectronic sensor further includes an ambient light compensation stage configured to reduce the share of current induced by ambient light in the current generated by the photodiodes.

[0010] Optionally, the subtractor stage and the summing stage also include an amplifier amplifying their respective output voltage.

[0011] Optionally, the optoelectronic sensor further comprises a filtering stage configured to filter the first and second electrical voltages.

[0012] Optionally, the optoelectronic sensor further comprises: - an emitting lens positioned opposite the light source so as to be traversed by the light beam emitted by the light source; and - a receiving lens arranged opposite the first and second photodiodes so as to be traversed by the fluxes received by the first and second photodiodes.

[0013] In a first option, the optoelectronic sensor is configured to detect an object in the predetermined detection zone when: a. The output voltage of the subtractor stage is positive when a light beam is emitted, and b. the output voltage of the summing stage is greater than a first predetermined voltage threshold when the light beam is emitted.

[0014] In the first option, the first voltage threshold is a hysteresis threshold having a lower and an upper terminal, the difference between the lower and upper terminals being greater than a predetermined voltage amplitude corresponding to a voltage amplitude due to noise on the output voltage of the summing stage.

[0015] In a second option, the optoelectronic sensor further comprises a controlled inverter stage and an integrator stage, the controlled inverter stage comprising: - a first controlled inverter connected to the subtractor stage and configured to invert the output voltage of the subtractor stage during the time intervals between the emission of two consecutive light beams of the time sequence of light beams; - a second controlled inverter connected to the summing stage and configured to invert the output voltage of the summing stage during the time intervals between the emission of two consecutive light beams in the time sequence of light beams; the integration stage comprising: - a first integrator connected to the first controlled inverter and configured to integrate the output voltage of the subtractor stage, partially inverted by the first controlled inverter stage, in order to obtain a subtractor detection signal; and - a second integrator connected to the second controlled inverter and configured to integrate the output voltage of the partially inverted summing stage by the second controlled inverter stage, so as to obtain a detection signal from the summing stage; and in which the optoelectronic sensor is configured to detect an object in the predetermined detection zone when: a. The subtractor detection signal is positive, and b. the detection signal of the summer is greater than a second threshold of determined tension.

[0016] The application also relates to a method for detecting an object in a predetermined detection zone by reflecting at least one light beam off the object using any of the examples of optoelectronic sensors presented in this disclosure, the method comprising: emit at least one beam of light within a predetermined time interval using the light source; obtain the output voltage of the subtractor stage during the predetermined time interval, the output voltage of the subtractor stage being composed of amplitudes generated by at least one light beam; to obtain the output voltage of the summing stage during the predetermined time interval, the output voltage of the summing stage being composed of amplitudes generated by at least one light beam from the sequence of light beams; and detect an object in the predetermined detection zone from the output voltages of the subtractor stage and the summing stage obtained.

[0017] Optionally, the method is implemented using an optoelectronic sensor according to the second option, and the method comprises: emit a time sequence of light beams within a predetermined time interval using the light source; obtain the output voltage of the subtractor stage during the predetermined time interval, the output voltage of the subtractor stage being composed of amplitudes generated by the light beams of the light beam sequence; process the output voltage of the subtractor stage by inverting the output voltage of the subtractor stage during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage to obtain a detection signal from the subtractor, from the first controlled inverter and the first integrator; obtain the output voltage of the summing stage during the predetermined time interval, the output voltage of the summing stage being composed of amplitudes generated by the light beams of the light beam sequence; process the output voltage of the summing stage by inverting the output voltage of the summing stage during the time intervals between the emission of two consecutive light beams in the time sequence of light beams, then integrating the partially rectified voltage to obtain a detection signal from the summing stage, using the second controlled inverter and the second integrator; and detect the object in the predetermined detection zone when: a. The subtractor detection signal is positive; and b. the detection signal of the summer is greater than a second threshold of determined tension.

[0018] The optoelectronic sensor and detection method examples presented in this disclosure thus make it possible to guarantee detection stability (object detected or not detected) by ensuring a sufficient signal-to-noise ratio, whether it be the electronic noise introduced by the various electronic components of the optoelectronic sensor, or the noise introduced by ambient light in the Current generation by photodiodes. In this case, the fact that the optoelectronic sensor described herein uses the output voltage of a summing stage, which adds the voltages from the currents generated by the first and second photodiodes when detecting an object within the predetermined detection zone, ensures detection stability by providing a sufficient signal-to-noise ratio to prevent noise-induced switching between detection and non-detection states. Furthermore, in the second example of an optoelectronic sensor based on the emission of a time-domain sequence of light beams to detect an object within the predetermined zone, the influence of noise on detection stability is further reduced.Indeed, noise on the voltages is filtered by the combination of the controlled inverter stage and the integrator stage, and the output voltages compared to detect or not an object (the detection signals) have an increased amplitude level compared to the first examples, which further increases the signal-to-noise ratio, thus improving the stability of the detection. Brief description of the drawings

[0019] Other features, details and advantages will become apparent upon reading the detailed description below and analyzing the accompanying drawings, in which: Fig. 1

[0020] [Fig.1] schematically represents an example of an optoelectronic sensor configured to detect the presence of an object in a predetermined detection zone by reflection of a light beam on said object. Fig. 2

[0021] [Fig.2] represents a schematic diagram of object detection by triangulation at starting from an example of an optoelectronic sensor. Fig. 3

[0022] [Fig.3] schematically represents another example of an optoelectronic sensor configured to detect the presence of an object within a predetermined detection zone by reflecting a sequence of light beams off said object. Fig. 4

[0023] [Fig.4] represents a logic diagram of an example of a detection method for a object in a predetermined detection zone by reflection of at least one light beam on the object using an optoelectronic sensor as described in this disclosure. Fig. 5a

[0024] [Fig.5a] represents a time evolution of the voltage signals measured in output of different electronic stages of an optoelectronic sensor in response to the emission of a time-lapse sequence of light beams when an object reflecting the light beams is positioned in a predetermined detection zone. Fig. 5b

[0025] [Fig.5b] represents a time evolution of the voltage signals measured in output of different electronic stages of the optoelectronic sensor in response to the emission of the same time sequence of light beams as that used in [Fig.5a] when the object reflecting the light beams is positioned beyond the predetermined detection area. Description of the implementation methods

[0026] An example of an optoelectronic sensor 1 configured to detect the presence of an object 10 in a predetermined detection zone by reflection of at least one light beam onto said object is now described with reference to Figures 1 to 3. The optoelectronic sensor 1 may be a background suppression sensor (known in English as "background suppressing sensors") that detects the presence of an object by triangulation.

[0027] The optoelectronic sensor 1 includes a light source 2 adapted to emit at least one light beam in a predetermined orientation. In the detailed examples below, the light source 2 is adapted to emit a time sequence of light beams. The light source 2 may, for example, be a light-emitting diode (LED). It is the reflection of at least one light beam on the object 10 that will allow its presence to be determined, notably by triangulation as explained later. Consequently, the predetermined detection zone Zd is defined according to the predetermined orientation of the light beam when using the sensor 1. A light beam may, for example, be a red light beam or an infrared light beam.

[0028] The optoelectronic sensor 1 comprises a first photodiode 3a and a second photodiode 3b. The first photodiode 3a is configured to generate a first electric current ia as a function of a first light flux received by the first photodiode 3a. Similarly, the second photodiode 3b is configured to generate a second electric current ih as a function of a second light flux received by the second photodiode 3b. Each of the photodiodes is connected to a ground of the optoelectronic sensor, as shown in [Fig. 3].

[0029] The optoelectronic sensor 1 includes a converter stage 4 configured to convert the first and second electrical currents, generated respectively by the first 3a and second 3b photodiode, into first va and second vh electrical voltages. The converter stage 4 thus converts the first electrical current i a, generated by the first photodiode 3a from the light flux it receives into the first electrical voltage v a. It also converts the second electrical current ih, generated by the second photodiode 3b from the light flux it receives into the second electrical voltage v h.

[0030] The optoelectronic sensor 1 includes a subtractor stage 5. The subtractor stage 5 is configured to generate an output voltage by subtracting the second electrical voltage vh from the first electrical voltage v a. The subtractor stage 5 may also include an amplifier for amplifying the output voltage of the subtractor stage. In some examples, the subtractor stage 5 may include an operational amplifier.

[0031] The optoelectronic sensor 1 includes a summing stage 6. The summing stage 6 is configured to generate an output voltage by adding the first electrical voltage va to the second electrical voltage v b. The summing stage 6 may also include an amplifier for amplifying the output voltage of the summing stage. In some examples, the summing stage 6 may include an operational amplifier.

[0032] The optoelectronic sensor 1 is configured such that the difference between the first luminous flux received by the first photodiode and the second luminous flux received by the second photodiode is positive when the light beam is reflected by an object positioned within the predetermined detection zone. Specifically, the relative positions of photodiodes 3a and 3b are determined such that the difference between the first luminous flux received by the first photodiode and the second luminous flux received by the second photodiode is positive when the light beam is reflected by an object positioned within the predetermined detection zone. The photodiodes are arranged side by side, contiguously, as shown in [Fig. 2]. The arrangement of the photodiodes 3 and the predetermined detection zone depend directly on the application in which the optoelectronic sensor 1 will be used.The optoelectronic sensor 1 presented can thus be used to detect an object passing at a given position opposite the sensor on a conveyor path. Examples include a suitcase moving on an airport conveyor belt or a part being moved on a production line.

[0033] In particular, and as illustrated in [Fig. 2], the presence of an object in a detection zone can be detected by triangulation from an electronic sensor 1. [Fig. 2] shows a schematic diagram of object detection by triangulation from an example of an optoelectronic sensor 1 according to this disclosure. It is a side view, perpendicular to the optical axis of the light beam emitted by the light source 2, of an example of sensor 1 when the object 10 is in the predetermined detection zone Zd (top representation), and when it is outside (bottom representation). The d axis represents the distance between sensor 1 and the object 10 to be detected, and the predetermined detection zone Zd extends between two extrema Zd1 and Zd2. The light source 2 of sensor 10 thus emits a light beam that first passes through an emitting lens 21, the beam is then reflected by the object 10, and then directed towards the photodiodes 3a and 3b by a receiving lens 31, an angle θ being formed between the light beam emitted by the light source 2 and the light beam reflected by the object 10. It is understood, as illustrated by [Fig. 2], that the angle θ varies according to the distance at which the object 10 is located relative to sensor 1, as does the luminous flux received by the photodiodes 3, which depends on this angle. In [Fig.[2] It is schematically shown that when object 10 is within the predetermined detection zone Zd, only the first photodiode 3a receives the reflected light beam, while when object 10 is outside the predetermined detection zone Zd, only the second photodiode 3b receives the reflected light. Object 10 is therefore detected when the first photodiode 3a receives the reflected light. However, this is a schematic representation intended to illustrate the detection principle used. In reality, the reflected light is received with varying intensity by both photodiodes 3 depending on the distance of object 10 from sensor 1. It is by comparing these light fluxes, via the currents generated by the photodiodes, that the optoelectronic sensor 1 is able to detect whether object 10 is within the predetermined detection zone Zd.Specifically, the extrema Zd2 is determined to correspond to an equivalent received luminous flux between the two photodiodes 3, such that when the object 10 approaches the sensor 1 along the optical axis from this extrema Zd2, the first photodiode 3a receives more reflected luminous flux than the second photodiode 3b, thus indicating the presence of the object 10 in the predetermined detection zone Zd. Conversely, when the object 10 moves away from the sensor 1 along the optical axis from this extrema Zd2, the first photodiode 3a receives less reflected luminous flux than the second photodiode 3b, indicating the absence of the object 10 in the predetermined detection zone Zd.

[0034] In the present disclosure, the optoelectronic sensor 1 is configured to detect an object in the predetermined detection zone Zd from the output voltages of the subtractor stage 5 and the summing stage 6.

[0035] In particular, in initial examples, the optoelectronic sensor 1 is configured to detect an object in the predetermined detection zone Zd when: a. The output voltage of subtractor stage 5 is positive when a light beam is emitted, and b. the output voltage of the summing stage 6 is greater than a first predetermined voltage threshold v th; during the emission of the light beams.

[0036] These first examples are shown in [Fig. 1] and can enable the detection of an object 10 in the predetermined detection zone using the emission of a single light beam emitted by the light source 2.

[0037] Thus, in these first examples, the optoelectronic sensor 1 may include a comparator stage 7 comprising a first comparator 7a configured to compare the output voltage of the subtractor stage 5 to a zero voltage and a second comparator 7b configured to compare the output voltage of the summing stage 6 to the first predetermined voltage threshold v th h. The optoelectronic sensor 1 may further include a logic gate 8 applying an AND function, receiving as input the outputs of the first 7a and the second 7b comparators, and transmitting a logic signal to a detection unit 9 triggering a detection of an object 10 in the predetermined detection zone Zd when the logic signal from the AND gate 8 that it receives is 1.

[0038] A positive output voltage of the subtractor stage 5 (condition a) corresponds to the fact that the first generated current ia is greater than the second generated current ib, which, theoretically, means that the luminous flux received by the first photodiode 3a is greater than the luminous flux received by the second photodiode 3b. Since the arrangement of the photodiodes 3 is determined so that a luminous flux received by the first photodiode 3a is greater than a luminous flux received by the second photodiode 3b when the object 10 is in the predetermined detection zone Zd, an object 10 should simply be detected in the predetermined detection zone when this condition is met. This is the detection principle explained above. This detection condition makes the detection distance of an object 10 in a predetermined detection zone Zd by the optoelectronic sensor 1 independent of the reflective nature of the object 10.Indeed, the detection principle used by the presented optoelectronic sensor 1 is based on a difference in luminous flux received by the photodiodes, such that even when the luminous flux is reflected by an object 10 with low reflectivity, for example, when the object is black, there will still be a difference in luminous flux received between each of the photodiodes 3 depending on the position of the object 10, even if the luminous flux received independently by each of the photodiodes is attenuated. In this respect, the presented optoelectronic sensor 1 makes it possible to detect an object 10 at a detection distance independent of the intrinsic reflectivity of the object 10 considered in this detection.

[0039] However, the inventors noticed that electronic noise introduced by the photodiodes 3 and the electronic stages of the optoelectronic sensor could induce A negative output voltage from the subtractor stage, even though the object to be detected was still within the predetermined detection zone, occurred after the object was first detected. This made the detection characteristics of the optoelectronic sensor potentially unstable. In other words, the inventors observed that the optoelectronic sensor could detect the presence of an object in the detection zone Zd at time t, and then detect its absence at time t+1 due to noise in the output voltage of the subtractor stage 5, making the interpretation of the object detection information relatively complicated.

[0040] Therefore, in the first examples, the optoelectronic sensor 1 is also configured to check condition b) before detecting an object 10 in the predetermined detection zone. As explained above, the optoelectronic sensor 1 according to this disclosure includes a summing stage 6 that adds the first va and second vh electrical voltages, and the optoelectronic sensor is further configured to compare this sum to the first predetermined voltage threshold vth / . Comparing whether the output voltage (va + vb) of the summing stage 6 is greater than the first predetermined voltage threshold vth / for detecting an object in the predetermined detection zone Zd ensures good detection stability by providing a sufficient signal-to-noise ratio.

[0041] Furthermore, verifying that the sum of the first va and the second vh electrical output voltages is greater than a threshold (v thl) also makes it possible to discriminate between a situation in which the object is positioned at a distance corresponding to the extremum Zd2 of the predetermined Zd zone for which the currents generated by the photodiodes are equal; and therefore the output voltage of the subtractor stage is zero; and a situation in which there is no object at all in front of the sensor, the light beam is therefore not reflected and the currents generated by the photodiodes are null, also inducing a zero output voltage of the subtractor stage.

[0042] In this measure, the summing stage 6 makes it possible to stabilize the detection of an object in the predetermined detection zone Zd by ensuring a signal-to-noise ratio sufficient to make a detection decision and also makes it possible to discriminate a situation in which the object is positioned at a distance from the sensor corresponding to the extremum Zd2 from a situation in which no object reflects the light beam.

[0043] In the first examples, the first predetermined voltage threshold vtbj can be determined from an average output voltage of the summing stage 5 when there is no object in the detection zone Zd and / or from an average output voltage of the summing stage 5 when there is an object beyond the detection zone Zd reflects the light beam. In particular, the first predetermined voltage threshold vth / can, for example, be set to be greater than a specified percentage of the average output voltage of the summing stage 5 when there is no object in the detection zone and / or greater than a specified percentage of the average output voltage of the summing stage 5 when there is an object beyond the detection zone Zd reflecting the light beam. In these initial examples, the first predetermined voltage threshold vth / j can be set to ensure a signal-to-noise ratio greater than a specified ratio. These alternatives guarantee the stability of object detection within the predetermined detection zone Zd by ensuring a sufficient signal-to-noise ratio on the output voltage of the summing stage 6 to satisfy detection condition b) presented above.

[0044] In examples, the first predetermined voltage threshold vthj is a hysteresis threshold with an upper and a lower limit. In these examples, the optoelectronic sensor is configured to detect the object in the predetermined detection zone Zd when the output voltage of the subtractor stage is positive and when the output voltage of the summing stage 6 is greater than the upper limit of the first predetermined voltage threshold vthj; during the emission of the light beams. In these examples, the optoelectronic sensor is also configured to interrupt object detection when the output voltage of the summing stage 6 is less than the lower limit of the hysteresis threshold of the first predetermined voltage threshold vthj; during the emission of the light beams.The lower limit of the hysteresis threshold can, for example, be determined from a maximum noise voltage generated by the sensor's electronic components on the output voltage of the summing stage 6. In particular, the lower limit of the hysteresis threshold can be determined such that the difference between the lower and upper limits is greater than a predetermined voltage amplitude corresponding to a voltage amplitude due to noise on the output voltage of the summing stage. This voltage amplitude due to noise on the output voltage of the summing stage can be predetermined from tests performed on the optoelectronic sensor.

[0045] In second examples, the optoelectronic sensor 1 considers a time sequence of light beams emitted by the light source 2 to detect whether or not an object is present in the predetermined detection zone. The light beam sequence refers to the emission, by the light source 2, of a plurality of light beams at a determined frequency. The time sequence of light beams is notably represented in Figures 5a and 5b by the reference numeral FL. Figure 5a represents a time evolution of the voltage signals measured at the output of different electronic stages of an optoelectronic sensor in response Figure 5b shows the temporal evolution of the same voltage signals in response to the emission of the time sequence of light beams when a light-reflecting object is positioned within the predetermined detection zone Zd.

[0046] In these second examples, the optoelectronic sensor 1 may include a controlled inverter stage 11 configured to invert the output voltage of the subtractor stage 5 and to do the same with the output voltage of the summing stage 6 during the time intervals between the emission of two consecutive light beams in the time sequence of light beams. The output voltage of the controlled inverter stage 11 acting on the output voltage (va - vb) of the subtractor stage is represented in particular in Figures 3, 5a and 5b by the reference V. As can be seen in Figures 5a and 5b, only the portions of the output voltage signals corresponding to the time intervals between the emission of two light beams in the sequence are inverted; the other portions of the voltage signals are not modified.In other words, the controlled inverter stage 11 applies a gain of -1 to the output voltages of the subtractor 5 and summing 6 stages during the time intervals between two consecutive light beams in the time sequence of light beams and does not modify the other parts forming these output voltages, which is equivalent to considering that the controlled inverter stage 11 applies a gain of 1 to these other parts.

[0047] The controlled inverter stage 11 may thus include a first controlled inverter lia connected to the output voltage of the subtractor stage 5 and configured to invert the output voltage (va - v*) of the subtractor stage 5 during the time intervals between the emission of two consecutive light beams in the time sequence of light beams. The controlled inverter stage 11 may also include a second controlled inverter 11b connected to the output voltage of the summing stage 6 and configured to invert the output voltage (va + vb) of the summing stage 6 during the time intervals between the emission of two consecutive light beams in the time sequence of light beams. The output voltage of the second controlled inverter 11b is thus represented by the reference V+ in [Fig. 3].

[0048] In the second examples, the optoelectronic sensor 1 may include an integrator stage 14 connected to the controlled inverter stage 11 and configured to integrate the output voltages V- and V+ of the controlled inverter stage 11. The integrator stage 14 may include a first integrator 14a connected to the first The controlled inverter 1 is configured to integrate the voltage V-, corresponding to the output voltage of the subtractor stage 5 (va - v*) partially inverted by the controlled inverter stage 11, so as to obtain a first detection signal VD!FF, called the "subtractor detection signal". The integrator stage 14 may also include a second integrator 14b connected to the second controlled inverter 11b and configured to integrate the voltage V+, corresponding to the output voltage of the summing stage 6 (va + v*) partially inverted by the controlled inverter stage 11, so as to obtain a second detection signal V SUM, called the "summing detection signal".

[0049] The subtractor detection signal is a label to designate the output voltage of the integrator stage 14, associated with the subtractor stage 5 of the optoelectronic sensor 1, while the summing detection signal is another label designating the output voltage of the integrator stage 14, associated with the summing stage 6 of the optoelectronic sensor 1.

[0050] In these second examples, an object 10 is detected in the predetermined detection zone Zd when: a. The detection signal of the subtractor V DIFF is positive; and b. The detection signal of the summer V sum is greater than a second threshold of voltage v th2 determined.

[0051] In these second examples, the optoelectronic sensor 1 may thus include a comparator stage of the integrator stage 12 comprising a first comparator 12a configured to compare the output voltage of the first integrator 14a of the integrator stage 14 to zero voltage and comprising a second comparator 12b configured to compare the output voltage of the second integrator 14b of the integrator stage 14 to the second predetermined voltage threshold vth2. The optoelectronic sensor 1 may further include in these examples the logic gate 8 applying an AND function and receiving as input the outputs of the first 14a and second 14b comparators, which is configured to transmit a logic signal to the detection unit 9 triggering the detection of an object 10 in the predetermined detection zone when the logic signal from the AND gate that it receives is high (1).

[0052] In these second examples, a temporal sequence of light beams is considered to detect whether an object 10 is present or not in the predetermined detection zone. In this case, the noise amplitude of the signal generated by the photodiode and the subsequent amplifier stages in response to a received light flux varies over time. Consequently, the noise amplitude of the signal generated by the photodiode and the subsequent electronic stages varies for each light beam in a sequence of light beams emitted by the light source 2. In this As a measure, partially inverting and then integrating the voltages generated at the output of the subtractor stage 5 and / or the summing stage 6 in response to the reception of several light beams emitted by the light source 2 makes the output voltages of the integrators less dependent on the variable noise that a single light beam could generate, since the noise variability is averaged by considering several beams. As such, the comparison of these output voltages to a threshold is much less dependent on the electronic noise introduced by the various elements of the optoelectronic sensor 1. In particular, and this is clearly shown in Figures 5a and 5b, it is understood that a voltage difference between a voltage signal V DIFF in a situation in which the object is positioned in the predetermined detection zone Zd ([Fig.5a]) and a voltage signal VD!FF in a situation in which the object is positioned beyond this area ([Fig.5b]) is all the greater as there are light beams in the time sequence of light beams so that confusion of these two situations due to electronic noise is largely reduced.

[0053] Furthermore, it is no longer necessary to synchronize the threshold comparisons with the emission of a light beam as proposed in the earlier examples. Indeed, the output voltages VD!FF and V sum of the integrator stage are continuous, so that once the time sequence of light beams has been emitted, and before these voltages are released for the emission of the next time sequence, the comparison of these voltages to their respective thresholds (zero voltage for V DIFF and V th2 for V SUM) can be carried out without the need to be precise about the instant at which these voltages are compared.

[0054] In these second examples, the second voltage threshold vlh2 is determined from the number of light beams emitted by the light source 2. In particular, in some examples, the second voltage threshold vth2 is a hysteresis threshold with an upper and a lower bound. In these examples, the optoelectronic sensor is configured to detect the object in the predetermined detection zone Zd when the detection signal of the subtractor VDIFF is positive and when the detection signal of the summing VSUM is greater than the upper bound of the second voltage threshold vth2. In these examples, the optoelectronic sensor is also configured to stop detecting the object when the detection signal of the summing Vsum is less than the lower bound of the hysteresis threshold of the second voltage threshold vth2.

[0055] In this case, the combination of the controlled inverter stage 11 and the integrator stage 14, which provides the detection signals for the subtractor VDIFF and the summing junction V, forms a synchronous demodulation stage for the sequence temporal demodulation of light beams. Indeed, the emission of a temporal sequence of light beams to detect the presence of an object within the predetermined detection zone Zd can be considered a way of modulating the presence or absence information of the object within the predetermined detection zone Zd across the different beams of the temporal sequence. Consequently, recombining the information from each of these beams, translated into voltages by performing a controlled inversion of these voltages and their integration, can be considered a synchronous demodulation of the object's presence or absence information.Furthermore, the combined use of the controlled inverter stage 11 and the integrator stage 14 also acts as a filter on a continuous external signal or one with a low frequency that would otherwise interfere with the first and second voltages generated by the reflected light beams of the sequence. Indeed, the controlled inverter stage 11, by applying a positive or negative unity gain to the sequence frequency, makes the interfering signal alternating, so that its integration by the integrator stage 14 is zero.

[0056] The optoelectronic sensor 1 according to this disclosure thus makes it possible to guarantee the stability of the detection while making negligible the difference in detection distance of an object by the sensor 1 when this object is low reflectivity or high reflectivity to the light flux.

[0057] The various examples presented in the following paragraphs of this disclosure may be combined independently with the first or second examples described above unless otherwise expressly stated.

[0058] In some examples, the optoelectronic sensor 1 includes an emitting lens 21, as shown in [Fig. 2]. The emitting lens 21 is positioned opposite the light source 2 so that the light beam emitted by the light source passes through it. It deflects the light rays of the light beam emitted by the light source 2 so that they converge at the output.

[0059] In some examples, the optoelectronic sensor 1 also includes a receiving lens 31, as shown in [Fig. 2]. The receiving lens 31 is positioned opposite the first 3a and second 3b photodiodes so that the fluxes received by the first 3a and second 3b photodiodes pass through it. The receiving lens 31 concentrates these light fluxes onto the photodiodes 3.

[0060] In some examples, the sensor 1 includes a signal amplifier stage capable of amplifying the first ia and second ib electrical currents or capable of amplifying the first va and second vh electrical voltages. The signal amplifier stage may, for example, be arranged between the photodiodes 3 and the converter stage 4. In this case, it will amplify the first ia and second ih electrical currents. The signal amplifier stage can also be placed between converter 4 and the summing 6 and subtracting 5 stages; in this case, it will amplify the first va and second vh electrical voltages. In examples where the subtracting 5 and / or summing 6 stages include an amplifier, there are therefore at least two signal amplifications: one applied to the currents or voltages, and one applied to amplify the output voltage of the subtracting 5 and / or summing 6 stages.

[0061] In some examples, the converter stage 4 is also an amplifier stage and includes a first transimpedance amplifier 41a capable of amplifying and converting the first electrical current ia into a first electrical voltage va and a second transimpedance amplifier 41b capable of amplifying and converting the second electrical current ih into a second electrical voltage v h. These examples allow, using the same electronic component, the amplification and conversion of a current into a voltage, thereby reducing the cost of the sensor and simplifying its design. In particular, the converter stage 4, with its first transimpedance amplifier 41a and second transimpedance amplifier 41b, can therefore correspond to the signal amplifier stage mentioned previously.

[0062] In some examples, the optoelectronic sensor 1 may include an ambient light compensation stage 13 configured to compensate for the current induced by the ambient light in the current generated by the photodiodes 3. In some examples, the ambient light compensation stage 13 may include a first compensation stage 13a connected in antiparallel to the first transimpedance amplifier 41a of the converter stage and a second compensation stage 13b connected in antiparallel to the second transimpedance amplifier 41b of the converter stage 4. More specifically, the first compensation stage 13a may include a first low-pass filter 131a connected to a first amplifier 132a, the first amplifier 132a being further connected to a first voltage-to-current converter 133a, as illustrated in [Fig. 3].Similarly, the second compensation stage 13b may include a second low-pass filter 131b connected to a second amplifier 132b, the first amplifier 132a also being connected to a second voltage-to-current converter 133b.

[0063] In examples, the optoelectronic sensor 1 may include a filtering stage F configured to filter the first va and second vh electrical voltages. The filtering is performed before these voltages are subtracted by the subtractor stage 5 or summed by the summing stage 6. The filtering stage F therefore comprises two filters. The filtering stage includes a first filter Fl to filter the first The electrical voltage is applied to obtain a filtered voltage vaF as shown in [Fig. 3]. The filtering stage F includes a second filter F2 to filter the second electrical voltage vh to obtain a filtered voltage vhF as shown in [Fig. 3]. The first and second filters are bandpass filters. These filters are essentially centered around the frequency of the light beam sequence in the second examples. In this way, the impact of spectral components induced by light sources other than the light source 2 of the optoelectronic sensor 1 on the first va and second vh electrical voltages is reduced. Since the detection of an object 10 in the predetermined detection zone is based on the exploitation of the first va and second vb electrical voltages, the detection is made more accurate.Furthermore, the bandpass filter also largely filters out the noise introduced by the electronic components used in the sensor on the first electrical voltage va and the second electrical voltage vb, in particular the noise introduced by the photodiodes 3, the noise introduced by the converter stage 4, and the noise introduced by the amplifier stage or the ambient light compensation stage 13, as applicable. Indeed, the noise can be considered essentially constant across all signal frequencies, so applying a bandpass filter to the voltages allows the spectral components of the noise outside the considered frequency band to be eliminated, which is small compared to the overall frequency range of the signal.

[0064] An example of a method 100 for detecting an object 10 in a predetermined detection zone by reflecting at least one light beam onto the object 10 using an optoelectronic sensor 1 according to this disclosure is now presented with reference to [Fig.4].

[0065] As illustrated by [Fig.4], the method 100 comprises an operation 110 of emitting at least one light beam in a predetermined time interval using the light source 2.

[0066] As illustrated in [Fig. 4], the method 100 comprises an operation 120 for obtaining the output voltage of the subtractor stage 5 during the predetermined time interval. The output voltage of the subtractor stage 5 is thus composed of amplitudes generated by at least one light beam emitted by the light source 2.

[0067] As illustrated in [Fig. 4], the method 100 includes an operation 130 for obtaining the output voltage of the summing stage 6 during the predetermined time interval. The output voltage of the summing stage 6 is also composed of amplitudes generated by at least one light beam.

[0068] As illustrated by [Fig.4], the method 100 includes an operation 140 of detecting an object 10 in the detection zone Zd predetermined from the output voltages of the subtractor stage 5 and the summing stage 6 obtained.

[0069] In particular, in first examples of a method 100 in which the optoelectronic sensor 1 with which the method 100 can be carried out corresponds to the optoelectronic sensor 1 according to the first examples described above, an object 10 can be detected in the predetermined detection zone when: a. The output voltage of the subtractor stage is positive during the emission of the light beams, and b. The output voltage of the summing stage is greater than the first predetermined voltage threshold when the light beam is emitted.

[0070] In second examples of method 100 in which the optoelectronic sensor 1 with which method 100 can be carried out corresponds to the optoelectronic sensor 1 according to the second examples described above, the operation 110 of emitting at least one light beam may include an operation 111 of emitting a time sequence of light beams in a predetermined time interval with the light source 2.

[0071] In these second method examples 100, the output voltage of the subtractor stage 5 and the output voltage of the summing stage 6 include amplitudes generated by the light beams of the light beam sequence.

[0072] In these second examples of method 100, the method 100 may further include an operation 131 for processing the output voltage of the subtractor stage 5 by inverting the output voltage (ya - ve) of the subtractor stage 5 during the time intervals between the emission of two consecutive light beams in the time sequence of light beams, and then integrating the partially rectified voltage (V-) to obtain the detection signal of the subtractor VD!FF. The detection signal of the subtractor VD!FF is therefore dependent on the number of light beams in the time sequence. It can be obtained from the first controlled inverter 1a of the controlled inverter stage 11 and the first integrator 14a of the integrator stage 14.

[0073] In these second examples of method 100, the method 100 may further include an operation 132 for processing the output voltage of the summing stage 6 by inverting the output voltage (ya + v*) of the summing stage 6 during the time intervals between the emission of two consecutive light beams in the time sequence of light beams, and then integrating the partially rectified voltage (V+) to obtain the summing detection signal VSUM. The summing detection signal VSUM is therefore dependent on the number of light beams of the time sequence. It can be obtained from the second controlled inverter 11b of the controlled inverter stage 11 and the second integrator 14b of the integrator stage 14.

[0074] Finally, in these second examples of method 100, the operation 140 of detecting an object 10 in the predetermined detection zone may further include an operation 141 of detecting an object 10 in the predetermined detection zone when: a. The detection signal of the subtractor V DIFF is positive, and b. the detection signal of the summer is greater than the second threshold of voltage v th2 determined.

[0075] Therefore, the optoelectronic sensor 1 and detection method 100 examples presented in this disclosure ensure detection stability by providing a sufficient signal-to-noise ratio, whether for electronic noise introduced by the various electronic components of the optoelectronic sensor or for noise introduced by ambient light in the current generation by the photodiodes. In this case, the fact that the optoelectronic sensor 1 according to this disclosure uses the output voltage of a summing stage 6, which adds the voltages from the currents generated by the first 3a and second 3b photodiodes in the detection of an object 10 in the predetermined detection zone, ensures detection stability (object detected or not detected) by providing a sufficient signal-to-noise ratio to prevent switching from one state to another due to noise.Furthermore, in the second example of an optoelectronic sensor 1 based on the emission of a time sequence of light beams to detect an object 10 in the predetermined area Zd, the influence of noise on detection stability is further reduced. Indeed, noise on the voltages is filtered by the combination of the controlled inverter stage 11 and the integrator stage 14, and the output voltages compared for detecting or not detecting an object, i.e., the detection signals VD1FF and VSUm, exhibit a higher level compared to the first examples, which further increases the signal-to-noise ratio, thus improving detection stability.

Claims

1. Demands Optoelectronic sensor (1) configured to detect the presence of an object (10) in a predetermined detection zone (Zd) by reflection of at least one light beam on said object (10), the optoelectronic sensor (1) comprising: - a light source (2) adapted to emit at least one beam of light in a predetermined direction; - a first photodiode (3a) configured to generate a first electric current (z fl) as a function of a first luminous flux on the first photodiode (3a); - a second photodiode (3b) configured to generate a second electric current (i è) as a function of a second luminous flux on the second photodiode (3b); a position of the first (3a) and second (3b) photodiodes is determined such that a difference between the first luminous flux received by the first photodiode (3a) and the second luminous flux received by the second photodiode (3b) is positive when the light beam is reflected by an object (10) positioned in the predetermined detection zone (Zd); - a converter stage configured to convert the first (ia) and second (z*) electrical currents into first (vfl) and second (vè) electrical voltages; - a subtractor stage (5) configured to generate an output voltage by subtracting the second electrical voltage (vb) from the first electrical voltage (vfl); - a summing stage (6) configured to generate an output voltage by adding the first electrical voltage (v fl) to the second electrical voltage (vb); in which the optoelectronic sensor further comprises a controlled inverter stage (11) and an integrator stage (14), the controlled inverter stage (11) comprising: - a first controlled inverter (lia) connected to the subtractor stage (5) and configured to invert the output voltage of the subtractor stage (5) during the time intervals between the emission of two consecutive light beams in the time sequence of light beams; - a second controlled inverter (11b) connected to the summing stage (6) and configured to invert the output voltage of the summing stage (6) during the time intervals between the emission of two consecutive light beams in the time sequence of light beams; the integrator stage (14) comprising: - a first integrator (14a) connected to the first controlled inverter (1la) and configured to integrate the output voltage of the subtractor stage (5) partially inverted by the first controlled inverter stage (lia), so as to obtain a subtractor detection signal (V diff);and - a second integrator (14b) connected to the second controlled inverter (11b) and configured to integrate the output voltage of the summing stage (6) partially inverted by the second controlled inverter stage (11b), so as to obtain a summing detection signal (V SUM); and wherein the optoelectronic sensor is configured to detect an object (10) in the predetermined detection zone (Zd) when: a. the subtractor detection signal (VD!FF) is positive, and b. the summing detection signal (V SUM) is greater than a second determined voltage threshold (v th2).

2. Optoelectronic sensor according to the preceding claim, comprising a signal amplifier stage capable of amplifying the first and second electrical currents or capable of amplifying the first and second electrical voltages.

3. Optoelectronic sensor according to any one of the preceding claims, wherein the converter stage (4) is also an amplifier stage and includes a first transimpedance amplifier (41a) capable of amplifying and converting the first electric current (i fl) into a first electric voltage (v fl) and a second transimpedance amplifier (41b) capable of amplifying and converting the second electric current (i *) into a second electric voltage (v *).

4. Optoelectronic sensor according to the preceding claim, further comprising an ambient light compensation stage (13) configured to reduce the share of current induced by ambient light in the current generated by the photodiodes.

5. Optoelectronic sensor according to any one of the preceding claims, wherein the subtractor stage (5) and the summing stage (6) also include an amplifier amplifying their respective output voltage.

6. Optoelectronic sensor according to any one of the preceding claims, further comprising a filtering stage (F) configured to filter the first (v fl) and the second (v è) electrical voltages.

7. Optoelectronic sensor according to any one of the preceding claims, further comprising: - an emitting lens (21) disposed opposite the light source (2) so as to be traversed by the light beam emitted by the light source; and - a receiving lens (31) disposed opposite the first (3a) and second (3b) photodiodes so as to be traversed by the fluxes received by the first and second photodiodes.

8. A method for detecting an object (10) in a predetermined detection zone (Zd) by reflecting at least one light beam off the object using an optoelectronic sensor (1) according to any one of the preceding claims, the method comprising: - emit (110) a time sequence of light beams in a predetermined time interval using the light source; - obtain (120) the output voltage of the subtractor stage (5) during the predetermined time interval, the output voltage of the subtractor stage (5) being composed of amplitudes generated by the light beams of the light beam sequence; - process (131) the output voltage of the subtractor stage (5) by inverting the output voltage of the subtractor stage (5) during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage to obtain a detection signal of the subtractor (V DIFF), from the first controlled inverter (1 la) and the first integrator (14a); - obtain (130) the output voltage of the summing stage (6) during the predetermined time interval, the output voltage of the summing stage (6) being composed of amplitudes generated by the light beams of the light beam sequence; - process (132) the output voltage of the summing stage (6) by inverting the output voltage of the summing stage (6) during the time intervals between the emission of two consecutive light beams in the time sequence of light beams, then integrating the partially rectified voltage to obtain a summing detection signal (V SUM), from the second controlled inverter (11b) and the second integrator (14b); and - detect (140) the object in the predetermined detection zone when: a. The subtractor detection signal (V DIFF) is positive; and b. the detection signal of the summing stump (V SUM) is greater than a second determined voltage threshold (v th2).

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